Energy Principle 4. Various sources of energy can be used to power human activities, and often this energy must be transferred from source to destination.

Teaching this principle is supported by seven key concepts:

4.1 Humans transfer and transform energy from the environment into forms useful for human endeavors. The primary sources of energy in the environment include fuels like coal, oil, natural gas, uranium, and biomass. All primary source fuels except biomass are non- renewable. Primary sources also include renewable sources such as sunlight, wind, moving water, and geothermal energy.

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4.2 Human use of energy is subject to limits and constraints. Industry, transportation, urban development, agriculture, and most other human activities are closely tied to the amount and kind of energy available. The availability of energy resources is constrained by the distribution of natural resources, availability of affordable technologies, socioeconomic policies, and socioeconomic status.
4.3 Fossil and biofuels are organic matter that contain energy captured from sunlight. The energy in fossil fuels such as oil, natural gas, and coal comes from energy that producers such as plants, algae, and cyanobacteria captured from sunlight long ago. The energy in biofuels such as food, wood, and ethanol comes from energy that producers captured from sunlight very recently. Energy stored in these fuels is released during chemical reactions, such as combustion and respiration, which also release carbon dioxide into the atmosphere.

4.4 Humans transport energy from place to place. Fuels are often not used at their source but are transported, sometimes over long distances. Fuels are transported primarily by pipelines, trucks, ships, and trains. Electrical energy can be generated from a variety of energy resources and can be transformed into almost any other form of energy. Electric circuits are used to distribute energy to distant locations. Electricity is not a primary source of energy, but an energy carrier.

4.5 Humans generate electricity in multiple ways. When a magnet moves or magnetic field changes relative to a coil of wire, electrons are induced to flow in the wire. Most human generation of electricity happens in this way. Electrons can also be induced to flow through direct interaction with light particles; this is the basis upon which a solar cell operates. Other means of generating electricity include electrochemical, piezoelectric, and thermoelectric.

4.6 Humans intentionally store energy for later use in a number of different ways. Examples include batteries, water reservoirs, compressed air, hydrogen, and thermal storage. Storage of energy involves many technological, environmental, and social challenges.

4.7 Different sources of energy and the different ways energy can be transformed, transported, and stored each have different benefits and drawbacks. A given energy system, from source to sink, will have an inherent level of energy efficiency, monetary cost, and environmental risk. Each system will also have national security, access, and equity implications.

What does this principle mean?

This principle discusses energy that is used for human purposes, including renewable and nonrenewable sources of energy, storage of energy, generation of electricity, and transportation of energy from place to place. Fossil fuels, which make up 82% of the US energy supply (2011, EIA), were originally derived from sunlight captured by ancient organisms millions of years ago. Biofuels are similarly derived from plants or algae but on a time frame of just a year or two. In both cases, burning these fuels releases carbon dioxide into the atmosphere, but burning fossil fuels releases carbon that has been stored underground for millions of years. Burning biofuels releases carbon that was recently pulled from the atmosphere and is commonly thought of as carbon-neutral.

This principle also addresses the practical and technological aspects of energy. The distribution of energy resources across the globe is uneven, as some regions have an abundance of energy sources while others do not. The areas where energy is used most intensively are not necessarily the same places where energy resources naturally exist. For example, rich oil and gas deposits are found in offshore marine environments and wind farms are located in rural settings. In both cases this energy is transported to a location where the energy is consumed. Moreover, the end uses of energy vary with geography, time of year, and time of day. Thus energy needs to be transported, stored and converted from one form to another so that it is available when and where it is needed.

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As oil resources become more scare, exploration pushes the boundaries of what is technologically possible, such as drilling in deep offshore waters.

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Why is this principle important?

There are numerous important ideas within this concept. It's essential that students understand where different forms of energy come from, as this predicates understanding of the impacts of energy use and decisions relating to energy policy.

In Energy Principle 3 students learn that ecosystems depend on the amount of energy available. This is also true for human societies; we are dependent on energy for infrastructure, transportation, food, and most other types of human activities. However, there are limits of how much energy is available to a given society. Even renewable forms of energy are dependent on geographic location and technological accessibility. Nonrenewable energy supplies are finite and create impacts from their extraction, transportation and consumption. Thus, students can begin to see how humans are dependent on using energy but are also constrained by the practicalities of energy use.

Another important consideration in this principle is that each source of energy has different benefits and drawbacks. There is no universal energy technology that will fit every need or solve every challenge. In Energy Principles 5 and 6 students examine decisions that affect the type of energy and amount of energy used by society, while Energy Principle 7 examines the quality of life resulting from energy choices.

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US Energy Information Administration data of energy sources in 2014. Image from the US Energy Information Administration.

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What makes this principle challenging to teach?

This principle addresses aspects of energy that are familiar to most students. However, students may hold misconceptions about where energy comes from or how much energy is derived from various sources. For example, students may be surprised to learn that only a small fraction of the US energy supply comes from wind turbines and other renewable sources (9%) while 82% is from fossil fuels. Nuclear power creates 9% of the US energy supply (Energy Information Administration, 2011). Despite the popularity and importance of renewable energy technologies, it's important to understand that fossil fuels make up the great majority of our energy supply, and it is forecast to remain that way for the coming decades (source: Energy Information Administration, 2013).

This illustrates the extraordinary challenges we face in moving beyond fossil energy. Transitioning away from fossil fuels will require us to use more of the other forms of energy, which brings about a new set of challenges. This problem is best understood with a quantitative approach so that students can grasp the scale of the challenge. While many students like the idea of wind energy, it is important to consider how many wind turbines it would take to replace the 82% of the energy supply that comes from fossil fuels, as well as the logistics of where to locate installations of wind turbines or other new energy infrastructure. A quantitative treatment of these subjects makes it clear how large a challenge we face in securing a dependable, safe and clean energy supply.

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Students look at a photovoltaic solar array on the roof of the high school during a renewable energy lab. The National Renewable Energy Laboratory sponsors the "Solar in Schools" program that has been adopted by Jefferson County School in Colorado. Photo by Dennis Schroeder / NREL.

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Strategies for teaching this principle

Energy supplies are located all across the globe, but students can begin to learn about these topics by investigating the sources of energy that power their own lives. The activity Power Source, asks teams of students to create a concept sketch of electricity that begins at the light switch and is traced back as far as they can go. This activity can be used with any grade level and it serves as an introductory activity that can prompt further exploration and can also reveal misconceptions.

Energy for You where students explore what types of energy resources exist in their state.

The energy blend of each region can be researched using EPA's energy grid data. With the activity From Grid to Home students analyze regional energy usage data and their own energy bills to gain an understanding of individual consumption, regional uses, costs, and sources of energy.

Students can also take on a case study approach to take on a detailed study of a particular energy type. For example, Biomass - Investigating Gases in which students generate biomass gases by heating wood pellets or wood splints in a test tube.

Related Pedagogic Methods

It is important to teach this principle using a quantitative approach, so that students gain a sense of scale with respect to how much energy is produced via different sources. This can help overcome misconceptions about how challenging it will be to replace non-renewable fossil fuels with other forms of energy.

College students can use EPA's eGRID database for detailed analysis of the energy blend of their hometowns. This database contains information about almost every electric power plant in the United States.

Another sources of data for college-level learning is the Energy Information Administration website. An abundance of data, maps, graphs and forecasts can be used to investigate a number of questions and create data-driven learning activities.

College students can also explore emerging sources of energy such as hydraulic fracturing. This complex issue can be addressed by using a case study or a role-playing approach. The activity Natural Gas and the Marcellus Shale illustrates how an unconventional reservoir rock can become an attractive hydrocarbon target.

College-level studies of energy sources once were the domain of traditional geology and engineering programs which focused on gas, oil, coal and uranium. But as energy technologies diversify and research in energy broadens, opportunities for studying energy exist within chemistry, agriculture, physics, biology, marine science, and atmospheric science. Moreover, the distribution and processing of fuels relates to multiple engineering fields, urban planning and economics. Thus, there are pathways to study energy resources within many different programs and majors.

eGRID - This EPA database is a comprehensive source of data on the environmental characteristics of almost all electric power generated in the United States. These environmental characteristics include air emissions for nitrogen oxides, sulfur dioxide, carbon dioxide, methane, and nitrous oxide; emissions rates; net generation; resource mix; and many other attributes.

Renewable Energy - This website contains summaries of various forms of renewable energy and is presented in a format that is readily readable by high school students.